We’ve all be stuck with a MetroCard with a whopping sub-cost-of-a-ride balance on it. Too little to swipe through a turnstile, too much money to just throw away. What to do, what to do? Some people know they can combine cards or add value to their card. A lot of people don’t know this and drop their cards or throw them away. So many people do this, in fact, that each year a fortune goes unspent and heads right back into the MTA’s coffers. Around $50 million per year. My, my MetroCard, indeed.

Stepan Boltalin, Genevieve Hoffman and Paul May of NYU’s ITP had an idea: What if those increments of nickels dime, quarters and dollars could be funneled to charity?

MetroChange is a charity donation platform using MetroCards. Inspired by farecard-to-charity projects in other cities, they set out to put those balances to good use. Once your hard earned coin makes it onto a MetroCard, it can only be used for NYC Subway and Buses. You can try to sell a card for its face value, but as anyone has attempted to do, its easier said than done and you look like a hustler. They sought a way to interface to the existing network to pull money from the card. Utilizing Arduino and off the shelf parts, they built a prototype machine for, lets call it, reverse fare collection – the leftover balances can be given to a charity of your choice. Theoretically you would go to a MetroChange terminal, swipe and the balance of the card gets transferred to charity fund.

The next step is making it go somewhere. And thats where it gets tricky. Plus the bonus amounts make it hard to discern between what was that sweet sweet coin and what was sweet sweet bonus. Despite the effort, for now, that money will stay stuck on the card.

Dont cry over spilled MetroCards.

The blogosphere and twitterverse exploded last month with excitement about MetroChange. It momentarily captured New York’s imagination. Its an ingenious solution to a slew of metropolitan questions – why can’t you get money back after putting it on a MetroCard? how can we make donating to charity easier? what happens to that extra cash? why is the bonus structure so weird? But most of all the public responded well to the idea that we can give these chunks of pocketchange to a good cause.